Aalborg Universitet Uplink Capacity Enhancement in WCDMA Multi Cell Admission Control, Synchronised Schemes and Fast Packet Scheduling Outes Carnero, José

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Aalborg Universitet

Uplink Capacity Enhancement in WCDMA

Multi Cell Admission Control, Synchronised Schemes and Fast Packet Scheduling Outes Carnero, José

Publication date:

2004

Document Version

Publisher's PDF, also known as Version of record Link to publication from Aalborg University

Citation for published version (APA):

Outes Carnero, J. (2004). Uplink Capacity Enhancement in WCDMA: Multi Cell Admission Control, Synchronised Schemes and Fast Packet Scheduling. Aalborg Universitetsforlag.

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Ph.D. Thesis

Uplink Capacity Enhancement in WCDMA

Multi Cell Admission Control, Synchronised Schemes and Fast Packet Scheduling

ISBN 87-90834-54-2 ISSN 0908-1224

R04-1011

Department of Communication Technology Institute of Electronic Systems

Aalborg University

Niels Jernes Vej 12, DK-9220 Aalborg Øst, Denmark

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Abstract

The large expectances created for WCDMA are based on its flexibility for multimedia capabilities and the high capacity it will provide. However, the demanded traffic grows rapidly, and new capacity enhancements are required in order to satisfy the future needs. This thesis analyses the potential for three advanced features to enhance the capacity in the uplink (from mobile station to base station) of WCDMA systems: multi cell admission control, synchronised schemes and fast packet scheduling.

First, a power-based multi cell admission control algorithm is studied as an alternative to the existing single cell algorithms. With a single cell algorithm the power increase caused by a new user is only evaluated in the serving cell before admission is granted/rejected. If the new user is close to the cell edge and requires high transmission power, it might also create excessive interference in neighbouring cells, leading to potential network instability. Multi cell admission control algorithms prevent these situations by also estimating the power increase at the neighbouring cells. The results reveal that under non-homogeneous load conditions, the uplink multi cell admission control offers 34% more cell throughput compared to a single cell scheme for a 5% probability of reaching an overload situation.

The second capacity enhancing feature consists of reaching uplink orthogonality by means of synchronised schemes. The performance of an uplink synchronous WCDMA system is evaluated at network level. According to the results generated for speech service, the main problem in uplink synchronous WCDMA systems is the code shortage. For ITU Pedestrian A environments with the most realistic assumptions, uplink synchronous WCDMA only provides a 10% capacity gain in terms of cell throughput. However, a high potential exists for situations where this code shortage can be solved, e.g. 36% capacity gain can be obtained assuming no code restriction. Variable modulation and coding is introduced as a solution to improve the channelisation code utilisation and thereby increase the capacity of uplink synchronous WCDMA. A 29% capacity gain is obtained in terms of cell throughput for a Pedestrian A environment.

Finally, a fast scheduling concept for packet data traffic over uplink dedicated channels is investigated including physical layer Hybrid ARQ (HARQ). Two algorithms for fast scheduling based on blind data rate detection and time division multiplexing with shorter scheduling period are considered. For comparable network load and user quality of service, the cell throughput becomes up to 9% higher with HARQ. The total gain of HARQ with a fast scheduling strategy based on channel quality information is 52% compared to 3GPP/Release 99-based packet scheduler implementations in a macro-cell scenario. In the case of a pedestrian micro-cell environment, the scheduling based on time division multiplexing can be combined with uplink synchronous WCDMA, providing a higher capacity increase. With an unfair scheduling policy there is a cell throughput increase of 108%, whereas with a strategy that allocates the same average throughput for all the users, the throughput increase remains as high as 95%.

The research has been carried out having as a reference study case the UMTS Terrestrial Radio Access (UTRA) Frequency Division Duplex (FDD) mode, standardised by the 3rd Generation Partnership Project (3GPP). The results provided in this thesis are supported by theoretical analysis and/or extensive system level simulations with multi cell scenarios, including the effect of many relevant mechanisms that have an impact on the radio access.

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Dansk Resumé

Translated by Troels B. Sørensen

De store forventninger til WCDMA er baseret på teknologiens fleksibilitet for multimedia transmission og trafikkapaciteten som tilvejebringes med denne teknologi. Trafikbelastningen vil dog vokse kraftigt og for at imødekomme fremtidige krav er det nødvendigt med nye teknikker til kapacitetsforøgelse. Denne afhandling analyserer potentialet i tre avancerede kapacitetsforøgende teknikker for uplink retningen (fra mobil enhed til basisstation) i WCDMA: multicelle netacces (’admission control’), synkroniseret transmission og pakkeskedulering (’packet scheduling’).

Indledningsvis studeres multicelle netacces baseret på modtagen effekt som et alternativ til de eksisterende enkeltcelle algoritmer. For enkeltcelle algoritmerne baseres netaccessen for en ny bruger udelukkende på forøgelsen af den modtagne effekt i den enkelte celle. Hvis den nye bruger er tæt på cellegrænsen og derfor kræver et højt transmitteret effektniveau er det sandsynligt at der også genereres kraftig interferens i nabocellerne; en sådan situation kan skabe et ustabilt netværk. Multicelle baseret netacces forhindrer sådanne situationer ved også at estimere effektforøgelsen i nabocellerne. Resultaterne viser at uplink multicelle netacces kan give en forøgelse i den supporterede trafikbelastning på 34% i sammenligning med enkeltcelle netacces under ikke-homogen trafik og 5% sandsynlighed for et overbelastet netværk.

Den anden kapacitetsforøgende teknik går ud på at opnå ortogonalitet i WCDMA uplink ved hjælp af synkroniseret transmission. Teknikken er i denne afhandling evalueret på netværksniveau. Som tydeliggjort med resultaterne for transmission af tale er det centrale problem for uplink synkroniseret transmission begrænsningen i antallet af spredningskoder:

Med de mest realistiske antagelser og udbredelsesmiljø i henhold til ITU ’Pedestrian A’ giver uplink synkroniseret transmission en beskeden kapacitetsforøgelse på 10% større supporteret trafikbelastning. Teknikken har dog et stort potentiale hvis det er muligt at omgå begrænsningen i antallet af spredningskoder – ideelt uden begrænsning i antal koder er kapacitetsforøgelsen på 36%. Variabel modulation og kodning er i denne afhandling anvendt til at forøge udnyttelsen af spredningskoderne og dermed forøge kapaciteten for uplink synkroniseret transmission i WCDMA. For ’Pedestrian A’ udbredelsesmiljøet er kapacitetsforøgelsen aktuelt på 29%.

Som den tredje og sidste teknik er der fokuseret på et hurtigt pakkeskeduleringskoncept for pakkedata trafik over dedikerede uplink kanaler, inkluderende retransmission på fysisk lag i form af ’Hybrid ARQ (HARQ)’. Specifikt er der fokuseret på to algoritmer baseret på henholdsvis ’blind data rate detection’, og ’time division multiplexing’ med kort pakkeskeduleringsperiode. For samme netværks trafikbelastning og bruger ’Quality of Service’ giver HARQ en forøgelse af den supporterede trafikbelastning på 34%. Kombineret med pakkeskedulering baseret på ’time division multiplexing’ og brug af ’Channel Quality Information’ er kapacitetsforøgelsen i makro-celle udbredelsesmiljø på 52% i sammenligning med pakkeskedulering baseret på 3GPP/Release 99. For mikrocelle udbredelsesmiljø kan skedulering baseret på ’time division multiplexing’ kombineres med uplink synkroniseret transmission og deraf følgende yderligere kapacitetsforøgelse. Anvendes en skeduleringsmetode der tillader differentiering af brugerne er kapacitetsforøgelsen på 108%, mens en metode der ikke differentierer brugerne giver en kapacitetsforøgelse på op til 95%.

Forskningen i denne afhandling er konkretiseret med UMTS Terrestrial Radio Access

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(UTRA) Frequency Division Duplex (FDD) standarden som reference. Denne standard er udviklet i 3rd Generation Partnership Project (3GPP). Afhandlingens resultater er genereret på baggrund af teoretisk analyse og/eller omfattende systemniveau simuleringer af multicelle radionetværk hvori er medtaget flere relevante aspekter med indflydelse på radiogrænsefladen.

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Preface and Acknowledgement

This Ph.D. thesis is the result of a three-year project carried out at the Center for PersonKommunikation (CPK), now integrated in the Department of Communication Technology of Aalborg University. The thesis work has been completed in parallel with the mandatory courses and teaching/working obligations required in order to obtain the Ph.D.

degree. The research project has been accomplished under the supervision of Research Professor Ph.D. Preben E. Mogensen (Aalborg University) and the co-supervision of Ph.D.

Klaus I. Pedersen (Nokia Networks) and Associate Professor Ph.D. Troels B. Sørensen (Aalborg University). This Ph.D. research has been fully sponsored by Nokia Networks.

The thesis investigates new techniques to increase the uplink capacity in WCDMA systems, concretely for UTRA FDD mode as specified by the 3rd Generation Partnership Project (3GPP). The study is mainly based on computer simulations, taking many practical system aspects into account. Theoretical analyses are also carried out in order to corroborate the results from the simulations. The reader is expected to have a basic knowledge about system level aspects of UMTS Terrestrial Radio Access Network (UTRAN) Frequency Division Duplex (FDD) as well as radio propagation.

The thesis is divided into three main parts, which can be read independently. Each of them is covered in a single chapter, except the one covering uplink synchronous WCDMA, which is relatively wider and is therefore distributed in three chapters. A list of abbreviations is provided at the beginning of the report. A large number of references are quoted throughout the dissertation. All of them are listed at the end of the report. A number of appendices have been included with additional information to clarify certain aspects associated with the main chapters of the report. Some of the appendices also include extra investigations that, although they do not directly lead to the final target, they provide interesting results related to the core of the Ph.D. thesis.

The work presented in Sections 6.3-6.5 has been jointly carried out together with Ph.D.

student Claudio Rosa (Aalborg University), to whom I must recognise fifty percent of the work, as well as unnumbered very interesting and productive discussions. The contribution of other colleagues to this thesis is described in Section 1.5.

I am deeply grateful to my supervisor Preben E. Mogensen for his support, advice and guidance, as well as for encouraging me to finish my Ph.D. thesis during the most difficult moments of the project.

From a technical point of view, I would also like to express my gratitude to Klaus I. Pedersen, who, apart from dedicating an important part of his time to the co-supervision of my thesis, has provided me with his excellent vision to conduct investigations and concentrate on the important matters. Distinctive gratitude is also paid to Troels B. Sørensen, who participated in the review process of this thesis report together with the rest of my supervisors, as well as for his wise pieces of advice during the study period, especially in the last phase. The contribution by Troels E. Kolding is very much appreciated, thanks to his technical support during part of the research, as well as his personal attention.

The support by all my colleagues and former colleagues from the Cellular Systems group of the University of Aalborg is highly appreciated. I would like to thank Lars Berger and Laurent Schumacher for their personal and technical support. The contribution of Claudio Rosa and Konstantinos Dimou, who I have worked in close cooperation with during the last part of my thesis, is not forgotten. Thanks also to Lisbeth S. Larsen for taking good care of me and for

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making my life easier during the moments when it was most necessary. A special acknowledgement is given to Pablo Ameigeiras, Isaías López and Juan Ramiro, who together with me studied at the University of Málaga and afterwards decided to continue tailoring our working future by trying new experiences in Aalborg.

I am also thankful to the rest of colleagues at Nokia Networks in Aalborg for their contribution to the elaboration of the Ph.D. study. I would like to dedicate a special acknowledgement to Jytte Larsen for reviewing the use of English in the report. Lise M.

Hansen’s assistance and good humour during the first two years of my Ph.D. study period are deeply appreciated.

I owe a special distinction to Gema, who decided to follow me to Aalborg, staying by my side, taking care of me and giving me all her love. I am infinitely thankful to my parents Pepe and Mercedes and my brother Daniel, to whom I have been in contact practically every day since I moved to Aalborg, and who have given me their unconditional love, advice, care and emotional support in the most difficult moments. I would also like to express my gratitude to the rest of my family and my friends in Málaga, who have never forgotten me and have made me feel closer to home thanks to their phone calls, letters, emails and visits to Aalborg.

José Outes Carnero March 2004

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Abbreviations

16QAM 16-symbol Quadrature Amplitude Modulation 3G 3rd Generation of mobile communications 3GPP 3rd Generation Partnership Project

64QAM 64-symbol Quadrature Amplitude Modulation 8PSK 8-symbol Phase Shift Keying

AC Admission Control

AVI Actual Value Interface

AWGN Additive White Gaussian Noise BER Bit Error Rate

BLER Block Error Rate

BPSK Binary Phase Shift Keying BRD Blind data Rate Detection

BS Base Station

BSC Base Station Controller BTS Base Transceiver Station

CCDF Complementary Cumulative Distribution Function CDF Cumulative Distribution Function

CDMA Code Division Multiple Access

CL Code Load

CN Core Network

DCH Dedicated Channel

DPCCH Dedicated Physical Control Channel DPDCH Dedicated Physical Data Channel

DS-CDMA Direct Sequence Code Division Multiple Access DTX Discontinuous Transmission

Eb/No Energy-per-bit to Noise ratio

Ec/Io Energy-per-chip to Interference-power-density ratio E-DCH Enhanced Dedicated Channel

Es/No Energy-per-symbol to Noise ratio FACH Forward Access Channel

FDD Frequency Division Duplex

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GPRS General Packet Radio Service

HSDPA High Speed Downlink Packet Access iid Independent, identically distributed IPI Inter-Path Interference

I-Q In-phase and Quadrature-phase L1 Layer 1 (physical layer) L2 Layer 2 (link layer) L3 Layer 3 (network layer)

LC Load Control

MAC Medium-Access Control MAI Multiple Access Interference

MC Multi Cell

MCS Modulation and Coding Scheme

ME Mobile Equipment

MRC Maximal Ratio Combining

MS Mobile Station

MSC Mobile Services Switching Centre MTPE Maximise Transmit Power Efficiency NBAP Node B Application Part

NR Noise Rise

NRT Non-Real Time

OVSF Orthogonal Variable Spreading Factor PAR Peak-to-Average (power) Ratio

PC Power Control

PDE Power Decrease Estimator PDF Probability Density Function PDP Power Delay Profile

PFT Proportional Fair Throughput PIE Power Increase Estimator QoS Quality of Service

QPSK Quadrature Phase Shift Keying RLC Radio Link Control

RM Resource Manager

RNC Radio Network Controller RNS Radio Network Subsystem

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RRC Radio Resource Control

RRFT Round-Robin Fair Throughput RRM Radio Resource Management

RT Real Time

RTPD Round Trip Propagation Delay RUF Resource Utilisation Factor

SC Single Cell

SF Spreading Factor

SGNS Serving GPRS Support Node

SHO Soft Handover

SIR Signal-to-Interference (power) Ratio SNR Signal-to-Noise (power) Ratio TAB Time Alignment Bit

TDD Time Division Duplex TDM Time Division Multiplexing TDMA Time Division Multiple Access TFC Transport Format Combination

TFCI Transport Format Combination Indicator TFCS Transport Format Combination Set TTI Transmission Time Interval TVM Traffic Volume Measurements

UE User Equipment

UMTS Universal Mobile Telecommunications System USIM UMTS Subscriber Identity Module

USTS Uplink Synchronous Transmission Scheme UTRA UMTS Terrestrial Radio Access

UTRAN UMTS Terrestrial Radio Access Network VMC Variable Modulation and Coding

WCDMA Wideband Code Division Multiple Access

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Chapter 1 Introduction

1.1 Preliminaries

Since the first analog cellular system was deployed in the beginning of the 80s [1], the mobile communication systems have been continuously evolving. The trend has been towards new technologies that offer more advanced services and an anticipated solution to the users’

demands. Currently two third generation of mobile communication (3G) systems are specified: the Universal Mobile Telecommunication System (UMTS) and cdma2000. UMTS is based on Wideband CDMA (WCDMA) and is composed of two different but related modes: UMTS Terrestrial Radio Access (UTRA) Frequency Division Duplex (FDD), and UTRA Time Division Duplex (TDD); cdma2000 consists of multicarrier CDMA [1].

The 3rd Generation Partnership Project (3GPP) is in charge of the specifications of the UTRA FDD, whereas a second body, 3GPP2, was established around cdma2000 [2].

In the beginning of this Ph.D. study, the 3GPP had already frozen the Release 99 specifications, and the preparation of a new release (Release 4) had already begun. Release 4 and 5 are currently frozen, whereas new releases (Release 6 and 7) are ongoing [3].

The evolution from the 3GPP/Release 99 is oriented to the increase of the cell capacity and peak data rate and the decrease of the delay associated with packet services [4].

Figure 1.1 illustrates the demanded data rates over the years for the uplink (connection from the mobile terminal to the base station) and the downlink (connection from the base station to the mobile terminal) [5]. Due to the asymmetrical properties of the traffic, most of the efforts to include a high data rate packet access in the 3GPP specifications are dedicated to the downlink. High Speed Downlink Packet Access (HSDPA) is the evolution of the Release 99

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Introduction

for downlink and provides peak data rates of up to 10 Mbps [6].

On the contrary, this thesis will focus on the uplink of WCDMA, but will consider the evolution of UTRA FDD mode as a reference study case. The main motivations for the selection of the scope of this Ph.D. thesis originate from the little attention paid to the uplink in the open literature compared to the downlink evolution of UMTS.

1.2 Overview of the UTRA FDD Release 99

1.2.1 Summary of WCDMA

WCDMA is a network-asynchronous wideband direct-sequence CDMA (DS-CDMA) scheme. The use of orthogonal variable spreading factors (OVSF) allows for the accommodation of highly variable user data rates and facilitates a flexible introduction of new services. The used chip rate of 3.84 Mcps leads to a carrier bandwidth of approximately 5 MHz. In UTRA FDD two separate bandwidth of 5 MHz are used for uplink and downlink. A user bit rate of up to 2 Mbps can be reached [7].

1.2.2 The Uplink in WCDMA

Due to their inherent properties, the design of the uplink and the downlink in WCDMA require different approaches. This sub-section describes the main characteristics of the uplink in WCDMA. The aim is to facilitate a better comprehension of techniques and approaches commonly used for the uplink, as well as to clarify the ways to proceed for the enhancement of the uplink. WCDMA defines two types of dedicated physical channels for the uplink, the Dedicated Physical Data Channel (DPDCH) and the Dedicated Physical Control Channel (DPCCH). Each connection is allocated one DPCCH and zero, one or several DPDCHs [8]. In addition, common physical channels are also defined. The channels use a 10 ms radio frame structure, divided into 15 slots. Within each slot, the DPDCHs and the DPCCH are transmitted in parallel I-Q branches, using different codes and spreading factors (SF). Figure 1.2 presents the generic structure of an uplink transmitter according to 3GPP [9], [10]. The

0 500 1000 1500 2000 2500

1997 2000 2005

Demanded data rate [kbps]

uplink downlink

Figure 1.1. Evolution of the traffic demand [5].

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signals are multiplied by a channelisation code (c) for channel discrimination and a scrambling code (S) for user discrimination. Additionally, the channels are given different relative power strengths by means of the power scale factor β. In the uplink the SFs can vary between 4 and 256 [7].

One inherent problem in the uplink is the so-called near-far effect: users near the receiver are received at higher power than those far away, which suffer degradation in performance.

Power control (PC) is the most common solution to solve the near-far effect. As a result, the signals received at the cell site from all the mobile units within a cell remain at the same level assuming equal bit rate [11]. In WCDMA fast closed-loop PC is run at slot basis, i.e. with a frequency of 1500 Hz.

In the uplink the reception of the signals in the same cell is performed in a centralised way by a unique entity, the base station (BS). Therefore, the equipment for reception is common for all the users and not distributed among the mobile stations (MS) as in the downlink case. This fact makes the use of advanced receivers in the uplink very attractive, since all the MSs can benefit from the technology upgrades made at the BS side.

The fact that the transmission is distributed among the MSs, with different physical locations, brings about both pros and cons. On one hand, the uplink of the WCDMA systems is not typically power limited, but interference limited.

On the other hand, since the signals from the different users in the cell arrive asynchronously at the BS, it is not possible to use orthogonal codes to reduce the multiple access interference

Σ

I

j cd,1 βd

Sdpch,n

I+jQ DPDCH1

Q cd,3 βd

DPDCH3

cd,5 βd

DPDCH5

cd,2 βd

DPDCH2

cd,4 βd

DPDCH4

cd,6 βd

DPDCH6

cc βc

DPCCH

Σ

S

Figure 1.2. Transmission of data through one or more DPDCHs and one DPCCH according to 3GPP [9].

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Introduction

UTRAN

RNS RNS

Core network

Circuit-switched core network

MSC

Packet-switched core network

SGNS

Iu

Iur Iub

Uu

UE UE UE UE

Cu Cu Cu Cu

RNC RNC

Node B Node B Node B Node B

ME ME ME ME

USIM USIM USIM USIM

(MAI), as it is done for the downlink. Furthermore, the packet scheduling gets complicated, as the users have to signal the information about their buffer occupancy.

The investigations in this thesis are carried out by assuming conventional Rake receivers. The Rake receivers are employed to exploit the multi-path diversity of the signals subject to multi- path fading. A Rake receiver consists of a bank of correlators, each of which correlates to a particular multi-path component of the desired signal. The correlator outputs may be weighted according to their relative strengths and summed to obtain the final estimate [12]. In this study, maximal ratio combining (MRC) is considered, which means that each of the branches associated with every multi-path component are used in a co-phased and weighted manner so that the highest achievable signal-to-noise ratio (SNR) is always available at the receiver.

Despite the fact that other advanced techniques can largely boost the overall performance of CDMA system, the Rake is still the receiver structure of choice for the first round of low- complexity receivers for 3G systems [13].

1.2.3 UTRAN Architecture

The UMTS system consists of a number of logical network elements, each of them with a defined functionality. The network elements are grouped in the UMTS Terrestrial Radio Access Network (UTRAN), the Core Network (CN), and the MSs, which in 3GPP are called user equipments (UE), as shown in Figure 1.3 [7]. The UTRAN handles all radio-related functionalities. The CN is responsible for switching and routing calls and data connections to external networks. The UE interfaces with the user and the radio interface.

Figure 1.3. UMTS architecture.

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The UMTS network elements can also be grouped in subnetwork elements. The UMTS standard is structured so that the internal functionality of the subnetwork elements is not specified in detail. Instead, the interfaces between the logical network elements have been defined.

The UTRAN consists of one or more Radio Network Subsystems (RNS) connected to the CN through the Iu interface. An RNS is composed of a Radio Network Controller (RNC) and one or more base stations, which in 3GPP are called Node Bs. A Node B is connected to the RNC through the Iub interface, and may serve one or multiple cells. It converts the data flow between the Iub and Uu interfaces and also participates in the radio resource management (RRM). The RNC owns and controls the radio resources in the Node Bs connected to it. In this thesis the term Node B is considered to refer to a site controlling one or more sectors. The term BS refers to the logical division of the Node B that controls one single sector. The difference between both concepts is illustrated in Figure 1.4.

The UTRAN permits, under certain circumstances, the use of multiple radio links across multiple cells in support of a single UTRAN-UE connection. This concept is referred to as soft handover (SHO).

In the CN, the Mobile Services Switching Centre (MSC) and the Serving GPRS Support Node (SGNS), serve the UE in its current location for circuit-switched and packet-switched services, respectively.

The UE consists of the Mobile Equipment (ME), which is the radio terminal used for radio communication over the Uu interface, and the UMTS Subscriber Identity Module (USIM).

1.2.4 Radio Resource Management

As the number of subscribers of mobile and wireless services raises, as well as the data rates required by their applications, the available resources have to be utilised efficiently.

RRM is thus a major concern for current as well as future network configurations. The main objective of the RRM is to efficiently utilise the available radio resources, while maintaining the quality of service (QoS) requirements from the users and the planned coverage area.

The RRM algorithms are: admission control (AC), load control (LC), packet scheduler (PS), resource manager (RM), handover control (HC) and PC. Figure 1.5 shows the location of the different RRM algorithms according to [7].

AC handles all the new incoming traffic and checks whether new connections can be admitted to the system. LC manages the situation in which the system load exceeds the planned value,

Figure 1.4. Difference between the concepts Node B and BS as defined in this Ph.D. thesis.

Area controlled by a Node B

Area controlled by a BS

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Introduction

and takes measures in order to get the system back to a feasible load. PS handles all the non- real traffic (NRT), i.e. packet data users, and decides when a packet transmission is initiated and what bit rate is to be used. RM controls the logical resources in the Node B and the RNC, and reserves resources in the terrestrial network. HC handles and makes the handover decisions, as well as controls the users’ active set of Node Bs. PC is responsible for keeping the radio link quality and minimising the power used in the radio interface by adjusting the transmission power. PC usually consists of a fast closed-loop PC algorithm and an outer-loop PC algorithm.

AC, LC, PS and RM are network based functions, since they are located in the RNC and control the resources of a Node B. Some fast actions associated with LC are run at the Node B side. PC and HC are connection based functions, since they handle the resources of one connection. HC is implemented in the RNC, while PC operates at the RNC, the Node B and the UE.

1.3 Techniques to Enhance the Uplink Capacity

So far, plenty of effort has been dedicated to the research of new techniques that increase the capacity of WCDMA. However, most of the work is concentrated in the downlink part, due to the asymmetrical properties of the traffic. The most important example is found to be HSDPA. Nevertheless, in spite of the asymmetry of the traffic between uplink and downlink there are reasons for investigating new capacity enhancing techniques for the uplink. On one hand, with the arrival of the application of the mobile communication systems to the multimedia communications, new services are getting into the picture. These services which will very likely require higher throughput and/or instantaneous data rate in the uplink direction from what the current implementations are able to provide: videoconferences, gaming, multimedia messaging, etc. Some examples of such services are included in Figure 1.6 [14]. On the other hand, the high peak data rate provided by HSPDA would have difficulties offering full service without an associated high speed reverse channel.

There are several approaches to exploit the peculiarities of the uplink in WCDMA and thus increase the capacity by means of new advanced techniques. The use of two receive antennas

Figure 1.5. Location of the different RRM algorithms.

I u b I u b

Uu Iub

UE Node B RNC

PC

AC LC

PS RM HC PC PC LC

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provides coverage gain by coherently combining the signals collected at each antenna.

Additionally antenna diversity provides gain against fast fading, since fast fading typically correlates poorly between the diversity antennas [7]. According to [7], the diversity gain in the ITU Pedestrian A channel is 7.5 dB in terms of required energy-per-bit to noise ratio (Eb/No) in the case without PC. In the ITU Vehicular A channel the diversity gain is smaller, 4.3 dB, because there is more multi-path diversity.

The performance of four-branch receiver antenna diversity is studied in [15], showing a 4 dB capacity gain with respect to two receiver antennas in Pedestrian A. In Vehicular A the gain is 3 dB. The more diversity is available, the smaller the diversity gain from an additional source of diversity [7]; e.g. in [16] it is concluded that with two receive antennas and fast closed-loop PC, multi-path diversity does not result in a capacity gain in micro-cells.

Another way to use antenna arrays is to form narrow beams towards the desired users, by means of the so-called beam-forming techniques [17]. This approach shows real promise for substantial capacity enhancement with the use of spatial and/or time processing at the cell site antenna array [18], [19], [20]. In [17], up to 350% capacity gain is obtained with eight antenna elements compare to the one antenna case from simulations with realistic assumptions. However, this gain is at the expense of an increased cost in the reception complexity as well as in hardware investment.

The enhancement of the RRM is also a solution to increase the uplink capacity in WCDMA systems. One of the ways is by means of the control of the received power at the Node B.

There are three algorithms involved in the control of the received power level: AC, LC and PS. These algorithms do not necessarily have to operate based on the received power level, but it is the most common approach for WCDMA systems [26], [27], [28], [29]. With a power based AC, users are accepted in the system if the estimated power increase due to the admission is not expected to exceed a certain value, i.e. if

threshold, P

P< (1.1)

where P is the total received power at the BS where the capacity is being requested, and Pthreshold is a power theshold chosen as a security margin, to prevent the system from reaching an instable state. By improving the liability of the AC algorithm it would be possible to reduce the security margin while keeping the same instability probability, and therefore increase the cell capacity. In [28] a power based AC is proposed for the uplink that evaluates the interference caused by the admission of the candidate user not only at the serving cell (single cell AC), but also at the neighbouring cells (multi cell AC). A multi cell AC algorithm can potentially avoid the problem of admitting a user that generates excessive interference in

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Mobile games Mobile intranet/office

extension Mobile shopping Mobile

music trafficMobile internet browsing Mobile

multimedia post card

Mobile PDA synchronisation

Mobile car navigation

Mobile online bill payment Mobile air bag

deployment

Mobile online airline reservation

Mobile internet chat

Source data rate [kbps]

uplink downlink

Figure 1.6. Traffic characteristics of 3G wireless data for advanced multimedia services [14].

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Introduction

an adjacent cell. However this typically happens when the user is close to the cell border and transmitting with a higher power level. In [30] a SIR based multi cell AC approach is presented; the final results do not show a significant capacity gain compared to an equivalent single cell AC under hot spot traffic. However, the results are obtained for speech services, which require a lower transmission power compared to higher data rate services. Hence, there is some potential from investigating the use of multi cell AC algorithms to increase the cell capacity in scenarios with high data rate services.

The mobile station (MS) has only information about its own chip sequence, while the BS has the knowledge of all the chip sequences for the own cell UEs. This opens for the utilisation of multi-user detection (MUD) in the uplink. With a MUD receiver, the information about multiple users is jointly used to better detect each individual user [21]. While in a conventional CDMA system all the users interfere with each other, in MUD all the users are considered as signals for each other [22]. MUD is a very attractive option to provide capacity increase in the uplink of WCDMA systems [21], [22], [23]. Furthermore, the use of MUD can also reduce the near-far effect [21]. The drawback of using optimal MUD is the increased complexity, so suboptimal approaches are commonly being sought [22].

Synchronising the received signals at the Node B can potentially increase the capacity in the uplink. The idea behind uplink synchronisation is to use a similar approach as in the downlink, where the signals from the same cell are separated by means of orthogonal codes, which allow reducing the MAI. The link level simulations in [24] show a 9 dB gain in signal- to-interference ratio (SIR) compared to an asynchronous scheme in an ITU Pedestrian A channel. However, these results are obtained for single cell, and they do not consider the blocking caused by the limited number of orthogonal codes. In [25] a theoretical value of 400% capacity gain is obtained by means of theoretical estimations in a pedestrian environment with two receive antenna diversity. These results are again based on a single- cell, without considering background noise. It seems quite obvious that there is some potential on the use of uplink synchronisation for capacity improvement. However, more thorough investigations with realistic assumptions are required in order to get a more exhaustive knowledge on the potential of such a scheme.

A potential capacity enhancement also exists for uplink packet access by improving the PS.

There are some investigations on the packet access for the uplink of WCDMA systems [29], [31], although in general it has been paid less attention than for the downlink case. One of the reasons is the already mentioned traffic asymmetry, as most of the demanded packet traffic is for the downlink. Furthermore, performing PS in the uplink is more complex, as the transmission is started from the users, and network needs signalled information on their buffer occupancy. Moreover, in order to perform power-based PS, the RNC needs measurements of the received power level at the Node B, which require some time until they are finally reported. This information is sent through Node B Application Part (NBAP) signalling at network layer. Hence, there is some significant delay from the moment in which the PS decisions are taken till they are actually effective. In [29], the potential of performing a faster PS is considered, showing some potential capacity gain. However this requires moving the PS to the Node B. This option, which is currently being considered in 3GPP [32], admits the design of new algorithms and advanced techniques for promising capacity increase of the uplink packet access.

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1.4 Objective of the Ph.D. Thesis

The objective of this Ph.D. study is to identify and analyse different methods for capacity enhancement in the uplink of WCDMA systems. Some of the most promising study frames from all those listed in Section 1.3 have been selected as study cases for this Ph.D. research.

Features such as multiple receive antenna diversity or MUD have already been investigated in detail. Therefore, the selection has been made taking into account the amount of work that has previously been done, as well as the potential for further investigations in each of the areas.

The goal is to provide results that help illustrating the potential of the chosen methods for capacity increase, but always taking into account the main issues derived from deploying such schemes. UTRA FDD mode is considered as a reference study case throughout the thesis.

The overall study includes the following general capacity enhancing schemes for the uplink of WCDMA:

• Multi cell admission control

In WCDMA systems the total received power generated in every cell gives a measurement of the uplink resources. A power-based AC allows access to the new users in the system provided that the estimated new power after the admission does not create excessive interference in the cell. However, with the arrival of the new services that require higher data rates, users might also create excessive interference in the adjacent cells. This problem has been formulated in the literature and some ideas have been proposed to solve it. In the beginning of the Ph.D. study no results showing a significant capacity increase existed from deploying a power based multi cell AC algorithm. However, a higher potential is expected in non-homogenous load conditions with high data rate services. In this thesis a new power-based multi cell AC is proposed and investigated, by identifying the situations in which it might be profitable to deploy.

• Uplink synchronisation

Preliminary studies on uplink synchronisation show a huge capacity increase by means of introducing uplink orthogonality and thus reduce the own cell MAI. However, the existing results on this topic were obtained under not very realistic assumptions, like the absence of thermal noise, perfect synchronisation or the use of single cell scenarios. Moreover, there are other aspects that have direct impact on the performance of uplink synchronisation and have not been investigated yet, like the constraints in the number of orthogonal codes. If such aspects are taken into consideration, the gain is expected to decrease.

In this Ph.D. dissertation the performance of uplink synchronous WCDMA is investigated by considering the most realistic assumptions. The goal is to calculate the real potential capacity gain while identifying the main issues that have an impact on it.

• Advanced fast packet scheduling

As already mentioned in Section 1.3, most of the efforts to improve the packet access in WCDMA systems have been concentrated on the downlink, on the so-called HSDPA within 3GPP. This thesis proposes and investigates several schemes that aim at increasing the capacity for uplink packet services and may potentially be included in

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Introduction

the uplink evolution for packet access in UMTS. Many of the studied ideas are based on techniques that have already been demonstrated to provide a very high capacity gain with HSDPA, like moving the PS functionality from the RNC to the Node B or the use of Hybrid ARQ (HARQ).

To sum up, this Ph.D. investigation aims at evaluating the system level performance of the three above-mentioned capacity enhancing methods for the uplink of WCDMA. Moreover, it will try to provide an answer to the question of whether it is worth deploying each one of them for different situations.

The results included in this Ph.D. thesis are based on theoretical analyses as well as static and dynamic computer simulations. The analysis of the cell capacity is more accurate and faster with theoretical calculations, but it complicates and sometimes is not feasible to carry out when considering realistic assumptions or advanced features, such as SHO, fast fading, traffic models, etc. This justifies the use of both static and dynamic system level simulators. A customised implementation of all the required simulators employed in this Ph.D. thesis has been carried out as part of the Ph.D. work. The system level simulations include link level results which are not part of this Ph.D. investigation and have been provided by others.

1.5 Structure of the Thesis and Novelty

Part of the Ph.D. work has been published in references [P1]-[P8], which are listed in Section 1.6.

The main part of the thesis is organised as follows:

Chapter 2 studies a multi cell AC approach as an alternative to the conventional single cell- based algorithm typically employed in WCDMA systems. Although the multi cell approach has already been addressed in the open literature, this thesis contributes with new system level results that explicitly compare its performance to a realistic reference case for the single cell admission control approach. Moreover, a new method has been derived to estimate the power increase that the admission of a new user causes in the neighbouring cells. The results have been obtained by means of static simulations. The elaboration of such a simulator implied both the implementation and design of a realistic network model. Part of the work is included in [P1]. The second author of the paper derived a modified version of the single cell power increase estimator (PIE), whereas the first author derived the multi cell PIE, developed the simulator and obtained the results. The rest of the authors provided guidance and corrections.

Chapters 3, 4 and 5 cover the investigation on uplink synchronous WCDMA.

Chapter 3 presents uplink synchronisation as a method to reduce the MAI in WCDMA systems. An overview of the scheme is given, and the main issues in the achievement of perfect synchronisation in the uplink are discussed. The study takes as a starting point the proposal made within 3GPP in [24]. This chapter of the thesis contributes with a feasibility study for uplink synchronous WCDMA, evaluating the problems related to the lack of synchronism as well as the impact of the radio channel on the orthogonality. Some of these issues are included in a 3GPP contribution [P6]. All the research work included both in Chapter 3 and [P6], counting theoretical studies, simulator development and results, has been performed by Ph.D. student José Outes, under the supervision of Klaus I. Pedersen and Preben E. Mogensen.

Chapter 4 analyses the performance of uplink synchronisation at system level, evaluating the

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impact on the results when it is applied in combination with other conventional capacity enhancing techniques, like SHO or discontinuous transmission (DTX). The lack of available channelisation codes is found to be the main drawback to reach a high capacity gain.

Prior to this Ph.D. research some system level results existed on potential gain of uplink synchronous WCDMA. However, such studies were only focused on the single cell case and neglected the background noise power. Chapter 4 provides both theoretical and dynamic simulation results at system level for realistic scenarios. The new research is included in [P2]

and [P5]. The first author performed the analytical study, carried out the network model design and the implementation of the dynamic system level simulator; finally he obtained the results. The implementation of the dynamic system level simulator also required an exhaustive network design in order to model a realistic scenario. The simulator relies on link level results, which have been provided by other colleagues. The rest of the authors contributed with guidance and a major part of the text writing and edition. Some of the preliminary results obtained from this investigation were also published in [P7] and [P8], and contributed to the decision made in 3GPP to discard uplink synchronisation from the standard.

Chapter 5 investigates the performance of uplink synchronisation combined with higher order modulation and coding rate as a solution to the channelisation code constriction problem. The evaluation is performed with the help of a theoretical analysis and an updated version of the system level simulator employed for the results in Chapter 4. New RRM algorithms for dynamic allocation of codes and modulation and coding schemes (MCS) have been designed and implemented in the simulator. Further link level modelling was necessary in order to also consider the new MCSs for the dynamic simulations. The work was published in [P3], and has been performed by the first author, with the guidance and corrections of the rest of the authors. The link level modelling was carried out with the support of Troels E. Kolding and Frank Frederiksen.

Chapter 6 presents and analyses the performance of advanced strategies for capacity enhancement of uplink packet access. The techniques are mostly based on moving part of the RNC functionality to the Node B, and include HARQ and fast scheduling based on blind data rate detection and on time division multiplexing with a shorter transmission time interval (TTI). Some of these techniques can also be combined in order to reach a higher capacity gain, as shown in this thesis. The novelty in this chapter consists of providing new results on the system level performance of HARQ with fast physical layer retransmissions, based on theoretical and dynamic simulation results at system level. Moreover, new algorithms to perform Node B PS in the uplink have been evaluated by means of the dynamic simulations.

The simulator employed to obtain the results is an upgraded version of the one used for Chapter 4, including traffic modelling and packet access, and has been jointly developed by Ph.D. students Claudio Rosa, Konstantinos Dimou and José Outes. Part of the work has been published in [P4]. The research has been carried out by the first two authors with equal contribution. Finally, a combined scheme for enhanced packet access including uplink synchronous WCDMA has been considered as well. All the work associated with the simulation results including uplink synchronous WCDMA have been provided by Ph.D.

student José Outes, under the guidance of his supervisors.

Chapter 7 summarises the main conclusions of the Ph.D. investigation.

Nine appendices have been included with additional information to clarify certain aspects associated with the main chapters of the report. Some of the appendices also include extra investigations that, although they do not directly lead to the final target, they provide interesting results related to the core of the Ph.D. thesis.

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Introduction

Appendix A investigates the performance of a multi cell admission control approach for the downlink case. The followed steps are the same as those presented in Chapter 1 for the uplink.

A new multi cell PIE for downlink has been derived by Ph.D. student José Outes; he also carried out the implementation of the static system level simulator, the required associated network model design, and the generation of the results. The reference single cell PIE for downlink was provided by Klaus Pedersen, who also supervised such a research together with Preben Mogensen.

Appendix B presents a new method to obtain uplink actual value interface (AVI) tables for different MCSs, which are essential to accomplish the simulation study in Chapter 5. The generation of the AVI tables relies on downlink results at link level provided by Frank Frederiksen. The procedure to obtain the uplink AVI tables has been derived by Ph.D. student José Outes under the guidance of Troels Kolding, Klaus Pedersen and Preben Mogensen.

Appendix C studies the impact of using a higher order modulation than BPSK on the peak-to- average power ratio (PAR) at the output of the uplink transmitter; the purpose of such a study is to better understand the inconveniences of using different MCSs for the investigation in Chapter 5. Statistical results on the PAR are provided for different transmission configurations based on Montecarlo simulations. The implementation of the simulator as well as the associated modelling of the uplink transmitters and the generation of the results have been carried out by Ph.D. student José Outes, under the guidance of Troels Kolding.

Appendix D proposes the use of an effective noise rise when uplink synchronisation is supported as a novel and more realistic load measurement compared to the conventional noise rise, normally employed for the uplink. The capacity gain of uplink synchronisation was evaluated theoretically in Chapter 5 by using the effective noise rise as a reference load measurement. The concept was proposed by Preben Mogensen, whereas the practical definition and theoretical expression of the effective noise rise have been provided by Ph.D.

student José Outes.

Appendix E describes the PIE for uplink presented in [26]; such a PIE has been used for the system level simulators in Chapter 2, Chapter 5 and Chapter 6.

Appendix F presents a new PIE for BSs supporting uplink synchronisation, serving both asynchronous and synchronous UEs simultaneously; such a PIE has been used for the system level simulators in Chapter 5 and Chapter 6. The PIE for uplink synchronisation has been derived by Ph.D. student José Outes.

Appendix G explains the basis behind the new uplink power decrease estimators (PDE) employed for the PS implemented in the system level simulator in Chapter 6. The PDEs have been derived by Ph.D. student José Outes.

Appendix H analyses the impact of using uplink AVI tables that include the effect of one DPDCH and one DPCCH on the simulations performed with HARQ in Chapter 6. The appendix also addresses the impact of using the same AVI tables for different data rates. The study has been carried out by Ph.D. student José Outes.

Appendix I summarises the source uplink traffic model implemented for the system level simulations with packet services in Chapter 6. The chosen traffic model has been obtained from a 3GPP technical report [32].

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1.6 Publications

The following articles have been written as part of the Ph.D. study:

[P1] J. Outes, L. Nielsen, K. Pedersen and P. Mogensen, “Multi-Cell Admission Control for UMTS”, IEEE Vehicular Technology Conference, Vol. 2, pp. 987-991, Rhodes (Greece), May 2001.

[P2] J. Outes, K. Pedersen and P. Mogensen, “Performance of uplink synchronous WCDMA at network level”, IEEE Vehicular Technology Conference, Vol. 1, pp. 105- 109, Birmingham (Alabama), May 2002.

[P3] J. Outes, K. Pedersen, P. Mogensen and T. Kolding, “Uplink synchronous WCDMA combined with variable modulation and coding”, IEEE Vehicular Technology Conference, Vol. 1, pp. 24-28, Vancouver (Canada), September 2002.

[P4] C. Rosa, J. Outes, K. Dimou et al, “Performance of Fast Node B Scheduling and L1 HARQ Schemes in WCDMA Uplink Packet Access”, Accepted for publication in the IEEE Vehicular Technology Conference, Milan (Italy), May 2004.

[P5] J. Outes, K.I. Pedersen and P.E. Mogensen, “Capacity Gain of an Uplink Synchronous WCDMA System Under Channelization Code Constraints”, Accepted for publication in the IEEE Transactions on Vehicular Technology.

Moreover, some of the preliminary results obtained during the Ph.D. study were presented as report documents to contribute in two 3GPP meetings:

[P6] TSGR1 (01) 0892: “System Level Performance of USTS”, by SK Telecom and Nokia.

[P7] TSGR1 (01) 1181: “System Level Performance of USTS” by Nokia.

The results included in [P7] have subsequently been included in the following 3GPP Technical Report:

[P8] 3rd Generation Partnership Project, “Study report for Uplink Synchronous Transmission Scheme (USTS)”, TR 25.854, Version 5.0.0, Release 5, Available at www.3gpp.org, December 2001.

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Introduction

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Chapter 2 Multi Cell Admission Control for Uplink

2.1 Preliminaries

The radio resource management (RRM) is responsible for the utilisation of the air interface resources, and it is necessary to guarantee a certain QoS, maintain the planned coverage area and offer a high capacity. Although most of the required RRM algorithms have already been designed (i.e. admission control, load control, power control, packet scheduler, etc.) not all of them have been optimised considering the nature of these new services [7]. This is the current situation of the admission control (AC) functionality, which has been studied widely, but there are still some aspects that could be refined in order to improve its performance.

From previous studies it is well known that power is a robust integral measure of the network load for WCDMA systems and normally used by AC [26], [27], [28], [30], [33]. In conventional single cell (SC) AC, users are allowed access and resources to the system provided that P<Pthreshold, where Pthreshold is a known power threshold obtained from network dimensioning, and P is the total transmitted/received power at the base station (BS) where capacity is being requested. If the condition is not kept, the network might reach an unstable situation, and the cell range is reduced; this only refers to the uplink case, which is typically interference limited, unlike the downlink case, which is mostly power limited. In order to decide whether a user should be granted capacity or not, the new power level at the BS of interest needs to be estimated, i.e. a power increase estimator (PIE) is required.

However, one of the shortcomings of this method is that the interference rise in the system

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Multi Cell Admission Control for Uplink

due to the new user is only evaluated for the cell of interest before admission is granted/rejected. In some cases a new user might also create excessive interference in the neighbouring cells (Figure 2.1), leading to potential network instability and resulting in dropped connections or lower quality of service (QoS). This is likely to happen in situations where the load in the cell of interest is low, while all the neighbouring cells are highly loaded, particularly if the new user is requesting a high bit rate. Such cases are especially critical in the uplink, where, as it has already been mentioned, the systems are mostly limited by the interference.

A new AC procedure is therefore investigated to prevent these situations from happening, which finally turns into making the system more stable and increasing the capacity while reducing the probability of reaching an overload situation. This is achieved by using a multi cell (MC) AC scheme, where information from the neighbouring BSs is considered in order to decide whether a new request should be accepted or not. Using such an approach is also discussed in [28], [30], [33]. In [28], the information from the neighbouring BSs is the pilot power received by the user equipments (UE), and in [30], the uplink signal-to-interference ratio (SIR) measurements at the adjacent BSs. In [33] the AC is carried out based on an empirical model where the measured received power is correlated with the traffic in the serving and the neighbouring cells.

In this chapter we propose an alternative power based MC AC algorithm for the uplink that takes into account the level of interference power received at the neighbouring BSs. The serving BS performs the AC by estimating the power increase that a new user would cause in the neighbouring BSs. The power increase estimation is carried out based on the information of the average interference level measured by the adjacent BSs and the information contained in the pilot report measurements that the UEs periodically send to the closest BSs [34].

The objective of this chapter is to analyse the benefit of the proposed MC AC method compared to an equivalent scheme exclusively based on SC information. This study focuses on the uplink case, although the same principles apply for the downlink; a similar approach for the downlink case is addressed in Appendix A.

The chapter is organised as follows: The MC AC algorithm is introduced in Section 2.2. The model used for simulating the operation of this procedure is outlined in Section 2.3.

Simulation results are shown and discussed in Section 2.4. Concluding remarks are presented in Section 2.5.

2.2 Power Based Multi Cell Admission Control

The noise rise (NR) is a parameter usually employed for uplink AC and is defined as the total received wideband power at the BS relative to the background noise power. Let us define a

Figure 2.1. Situation where a new UE generates extra interference at a neighbouring cell.

Serving cell Neighbouring cell #j

hserv hneigh,j

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SC power based admission criterion for the uplink as

TH,

serv NR

NR < (2.1)

where NRserv is the noise rise at the serving BS after the user has been admitted to the system, and NRTH is the noise rise value where the system is considered to reach the overload situation, set from network dimensioning. The serving BS is chosen as the BS with the lowest propagation path loss to the UE. Since it is not possible to know the final NR before the addition of the user, the following condition is assessed to take the admission decision

,

target[dB]

offset TH

est

serv NR NR NR

NR < − = (2.2)

where NR^estserv is an estimate of NRserv, and NRoffset is a noise rise offset set to compensate for potential estimation errors. If NRTH is exceeded, load control (LC) actions have to be carried out. Figure 2.2 shows the areas in which a BS can operate. While the BS is working in the feasible area, new users can be admitted according to the AC algorithm. When the system is operating in the marginal load area, then preventive LC actions are taken, which means that no more users are accepted in the system. If the BS receives power to such an extent that it reaches the overload area, LC actions are taken to reduce the system load.

Nevertheless, this AC algorithm does not consider the problem of making an adjacent BS reach an overload situation because of the admission of a new user in the serving cell. To avoid these situations an MC AC algorithm is proposed, where a new user is admitted to the system if the noise rises of the serving and all its adjacent BSs do not exceed the target value, i.e. provided that

and

TH ,

serv NR

NR <

, 1

|

,j TH adj

neigh NR j j N

NR < ∀ ≤ ≤ (2.3)

where NRneigh,j is the noise rise at the j-th adjacent BS after the user has been added to the system, and Nadj is the number of adjacent BSs. The serving BS is the one labelled as serv, and the Nadj adjacent ones from neigh,1 to neigh,Nadj, as shown in Figure 2.3 for a grid with 1-sector sites.

Again, as it is not possible to know the final NR beforehand, an estimate is applied and the admission criterion is modified to

and

target ,

est

serv NR

NR <

, 1

|

, target adj

est j

neigh NR j j N

NR < ∀ ≤ ≤ (2.4)

where NR^estneigh,j is an estimation of NRneigh,j.

Figure 2.2. Uplink operating areas in a BS.

Load

NRoffset

NR NRTH

NRtarget

∆load

Overload area Marginal load area Feasible load area

Aalborg Universitet Uplink Capacity Enhancement in WCDMA Multi Cell Admission Control, Synchronised Schemes and Fast Packet Scheduling Outes Carnero, José

Ph.D. Thesis

Uplink Capacity Enhancement in WCDMA

Abstract

Dansk Resumé

Preface and Acknowledgement

Contents

Abbreviations

Chapter 1 Introduction

1.1 Preliminaries

1.2 Overview of the UTRA FDD Release 99

1.2.1 Summary of WCDMA

1.2.2 The Uplink in WCDMA

Σ

Σ

1.2.3 UTRAN Architecture

1.2.4 Radio Resource Management

1.3 Techniques to Enhance the Uplink Capacity

UE Node B RNC

1.4 Objective of the Ph.D. Thesis

1.5 Structure of the Thesis and Novelty

1.6 Publications

Chapter 2 Multi Cell Admission Control for Uplink

2.1 Preliminaries

2.2 Power Based Multi Cell Admission Control